Distributed Orthogonal and Quasi-Orthogonal Space-Time Block Code with Embedded AAF/DAF Matrix Elements in Wireless Relay Networks with Four Relays

摘要

We consider cooperative networks of one source, four relays, and one destination. Each of them has a single antenna. The four relays use a proposed full rate distributed quasi orthogonal space time block code (DQOSTBC) scheme. If the channel state between the source and a relay is above a threshold, we select the elements of the DQOSTBC matrix to be the decode-and-forward (DAF) type; if it is below the threshold, the corresponding elements are the amplify-and-forward (AAF) type. Thus the proposed scheme is a DQOSTBC matrix with embedded adaptive DAF/AAF elements. The bit error rate (BER) simulation results show that the proposed DQOSTBC is approximately 7dB better than the traditional DQOSTBC (all matrix elements are fixed as DAF type) at a BER of 10~(-3) because traditional DQOSTBC loses full diversity due to errors in the information received. The proposed DQOSTBC is about 3 dB better than the rate 1/2 DOSTBC also proposed with adaptive DAF/AAF matrix elements at a BER of 10~(-3) at the same spectral efficiency of 2bits/s/Hz.